Inflammatory bowel disease (IBD) is a complex multifactorial disorder in which epithelial defects and inappropriate immune responses to commensal microbiota lead to chronic mucosal damage of the gastrointestinal (GI) tract. IBD is associated with high morbidity and substantial financial burden, yet current therapies produce significant side effects with limited therapeutic options for non-responsive patients. Although many cytokines are linked to IBD pathogenesis, tumor necrosis factor (TNF) has received much attention as a therapeutic target. TNF is also a protective factor in intestinal homeostasis and IBD, as evident from published findings and preliminary data included in this application. While TNF signals through receptors (TNFR1 and TNFR2), their individual and tissue-specific roles in intestinal health and disease are unclear. Our group, which has been at the forefront of defining the protective roles of TNF in the GI tract, reported that TNFR1 and TNFR2 promote GI epithelial cell survival, restitution, and regeneration. Furthermore, recent studies and preliminar data included in this application show that TNFR1 and TNFR2 promote epithelial integrity in mice and protect against the development of colitis, microbial dysbiosis and sequelae, such as colitis-associated cancer. This suggests that that TNF signaling provides a critical reparative cue for the GI tract following injury. We will test the novel hypothesis that receptor-specific (TNFR1 vs. TNFR2) and cell type-specific (epithelial vs. immune cell) mechanisms determine protective effects of TNF in the colon and define potentially novel therapeutic targets. The following Aims are designed to address this overall hypothesis: 1. By using novel mouse and human reagents targeting receptor expression in injury and inflammation models, we will determine the role of intestinal epithelial TNFR1 and TNFR2 in epithelial regeneration and colitis, 2. Determine how TNFR1 and TNFR2 in specific immune cell subtypes regulate colonic inflammation and dysbiosis through epithelial and immune cell compartment disruption of respective receptor signaling and microbiome and metabolome profiling, and 3. Determine how TNFR transcriptional targets regulate intestinal epithelial regeneration, and how these targets can be applied to identify novel IBD therapies through computational modeling, high throughput screening, mouse models and human cell and enteroid culture. Thus, these studies will provide a significant advance in the field, by defining the cellular and tissue compartments of TNFR1- and TNFR2-based anti-inflammatory and homeostatic mechanisms and create a roadmap for developing potential new therapeutic targets and repositioning existing compounds to bring to bear on colitis and colonic homeostasis.